For mono crystalline or polycrystalline materials the DRX proves

because in the spectrum of mono-crystalline material there is only one peak on the other hand in the spectrum of polycrystalline material exists several peaks

Please have a look at the answers of a similar question some time ago here on RG:

https://www.researchgate.net/post/What_is_the_best_way_to_confirm_that_I_am_having_a_single_crystal_or_poly-crystalline_material_using_different_characterization_techniques?_iepl%5BgeneralViewId%5D=x6k8p6PJZ3yS1HfwErw3RdBw1eJuL6hJ80kL&_iepl%5Bcontexts%5D%5B0%5D=searchReact&_iepl%5BviewId%5D=ggQIuFNvbp1vrLNz1GGf1S3tUCwgdN9prVQu&_iepl%5BsearchType%5D=question&_iepl%5Bdata%5D%5BcountMoreThan20%5D=1&_iepl%5Bdata%5D%5BinteractedWithPosition5%5D=1&_iepl%5Bposition%5D=5&_iepl%5BrgKey%5D=PT%3A52d783b3d4c11816198b467a&_iepl%5BtargetEntityId%5D=Q%3A52d783b3d4c11816198b467a&_iepl%5BinteractionType%5D=questionView

Thanks to everyone.

@ Abdelkader Hafdallah sir, DRX? are you saying XRD? Sir, I am attaching my XRD here. Please have a look and suggest.

Use image J Software to calculate crystallite/grain size from TEM analysis.

Crystallite and particle size are different and these are calculated based on application/requirement. A crystallite is dimension of single crystal of same orientation, but a particle is bigger one (agglomeration/accumulation of crystals) it can be called as grain. Crystallite size can be calculated from XRD and TEM and both should match, but on the basis of this one can not say it's single or polycrystalline. Your XRD graph is showing polycrystalline behavior, different crystal structures are present (101,110,111,002,200,211,220, etc). To get Particle size DLS can be used provided the solid powder is dispersed uniformly in solvent and mixture is transparent.

Single crystal has a high degree of order in which the crystal lattice of the entire sample is continuous with no grain boundaries. While A polycrystalline materials are composed of plentiful individual grains of crystallites. The XRD pattern presented is for poly crystalline solid.

Single crystalline materials contain single grain boundaries with single orientation. Hence you will get single peak in XRD. Polycrystaline materials consists of many grains with different orientations. Hence you will get many peaks with different orientations in XRD. XRD is the basic tool to analyse the crystalline materials. TEM is also possible to confirm the polycrystaline nature of the materials.

Hello Pallab,

You cannot compare crystallite size (size of single crystal) with grain size (agglomeration of crystallites).

It is not easy to prove wether your XRD is from single crystal or not? I think it is not. The easy way to check it - just take the polycristalline SnO2 sample and measure its XRD. Compare the both XRDs and if the you'll find the same lines in both patterns this will prove that your 1st pattern was obtained from polycrystalline sample.

If we are speaking, for example. about metals, then grain=crystallite. The same is true for most nanoparticles... If we are speaking about micro-particles, then usually particle>crystallite. But I think original poster does not need any answers anymore.

With your SAED result, you can say it may have single crystal nature in the selected area, but not for the whole material.